Abstract: An explosive actuated acoustic device emits sound to be used in torpedo countermeasures. Numbered devices are delivered over an extended area and sink through the water. The devices are actuated at different times as they sink, to provide sound masking over an extended period of time. The devices also include safety devices which prevent premature actuation from jarring or jolting and from impact with the water.

Abstract: An underwater sound source with a remote controlled actuator comprising a oy having a buoyant portion, a plurality of launch tubes storing acoustic charges, a radio transceiver, control circuitry, hinged doors at the bottom of the tubes, and a safety release circuit. The hinged doors are secured by pneumatic actuators to allow a selected door to open on a radio signal from a remote location. The charges are pressure sensitive and will explode at a preselected depth. A launch platform can deploy the device and remove itself from the general vicinity of the test site. The device releases the charges on command from a transmitter aboard a vessel and reports on the status of the launch tube doors to a receiver aboard a vessel. A safety valve can be opened automatically or on power failure to insure that all acoustic charges have been discharged.

Abstract: A method for determining a far-field signature FF(t) of a plurality of N seismic sources Si (i=1, . . . , N) comprises a stage of measuring a near-field signature NFi(t) of each seismic source Si. In a preliminary stage an initial near-field signature NFio(t) of each seismic source Si and an initial far-field signature FFo(t) of the plurality of N seismic sources are measured simultaneously. An operator G is determined, defined by the convolution integral ##EQU1## The near-field signature NFi(t) measuring stage is carried out on each firing of the N seismic sources Si.

Abstract: A closed-cycle combustion low-frequency acoustic pulse source for use underwater. An elongated combustion chamber, having a first end and a second end and an elongated elastic sleeve, is filled with a stoichiometric mixture of oxygen and hydrogen from an electrolyzer. When the mixture is ignited at the first end of the chamber, a longitudinally traveling flame front is initiated at the first end of the chamber. The moving front results in a traveling thermal pressure pulse. The pressure pulse is communicated to the surrounding underwater medium producing a generally uni-directional acoustic pressure pulse along the longitudinal axis of the elongated chamber. An alternative embodiment utilizes an array of sources disposed along the generally horizontal longitudinal axis of the array.

Abstract: A termination assembly is disclosed providing a substantially watertight, yet field serviceable interface to a plurality of electrical splices. The termination assembly includes a housing having an anchor portion for receiving and fixing a multi-transmission line cable therein, a ported sleeve for cradling the transmission lines, and a shell for providing field access to the splices between the transmission line in the interior of the housing. A resinous epoxy, together with O-ring seals and heat shrink tubing provide redundant protection against the invasion of water into the housing along the transmission lines.

Abstract: The present invention relates to a method and device for discharging an electric current between two electrodes, comprising considerably reducing the resistance to the passage of electric current at least between the electrodes so as to bring it to a resistance value near to or slightly higher than the critical resistance by interposing a conductive electrolyte between electrodes. This improves the rate of discharge of an electric current produced between the electrodes, by eliminating substantially completely the latency time.

Abstract: A seismic pulse generator comprises a body 1 having an internal gas-pressurizable first chamber 2 adjoining a second chamber 6 for containing a fluid. A flap valve member 21 is rotatable about a pivot axis for closing a bore 24 communicating with the first chamber. A latch 22 releasably retains the flap valve member in the closed position and a gas operated piston 13 slidably moves within an associated cylinder 12. When the first chamber 2 is pressurized with gas and the flap valve member 21 is released from its closed position to uncover the bore 24, the piston 13 moves to cause communication between the chambers 2,6 and generation of a shock wave in the second chamber. The second chamber has outlet means 7 to permit a pulse of energy to be transmitted from the second chamber in response to the shock wave generated in the second chamber.

Abstract: A towable marine seismic source apparatus for producing a high resolution seismic signal at relatively shallow depths for engineering surveys is disclosed. The apparatus support frame operably mounts a plurality of eight identical chambered air guns in a 2.times.4.times.2 configuration to provide a tapered, heavy centered point source. The cylindrical air guns are positioned in a horizontal orientation at a predetermined depth of 1 to 3 meters and are synchronized to fire substantially simultaneously to achieve maximum peak energy output. Two chamber sizes of individual air guns (4 cu. in. & 10 cu. in.) are in a desired range and may be preferably employed in the array configuration to produce the seismic signal having distinct signature characteristics.

Abstract: A method for extrapolating the far field signature of a seismic sound source array from near field measurements, by taking into consideration, the instantaneous firing and environmental parameters that exist locally for each individual sound source in the array.

Abstract: In order to accumulate data from which the signature of an array of n interacting seismic sources 21 to 27, for instance marine seismic sources in the form of air guns, can be determined, the array is actuated and the emitted pressure wave is measured at n independent points whose positions will respect to the array are known by hydrophones 31 to 37. Data from the measured pressure wave is stored for subsequent processing to produce n equivalent signatures of the n sources taking into account the interactions therebetween. The signature of the array is then determined merely by superposing the n equivalent signatures.

Abstract: A novel device and method are provided herein for the production of underwater sound. This device, termed a plasma jet underwater acoustic source includes a central electrode and a concentric insulator having a longitudinal bore to accommodate the central electrode, the bore being spaced from the central electrode by a longitudinally-extending annular chamber. A plasma cavity is bounded at its upper end by the central electrode, and is in communication with the annular chamber. The cavity is adapted to be connected to a gas supply, so that it may be filled with gas. An outer housing of electrically-conductive material surrounds the insulator and terminates in a centrally-apertured end plate whose central aperture provides an extension to the plasma cavity, the end plate being adapted to be grounded.

Abstract: The novel method substantially reduces the pressure pulse generated by an implosion of a cavity within a body of water by aborting the implosion. The abortion of the implosion is produced by generating within the cavity an explosion at the instant that this cavity attains its maximum volume.The method can also be used to generate within a body of water an impulsive acoustic signal by generating a first explosion within the body of water to produce therein a powerful pressure pulse and a cavity of very low pressure, and then generating a second explosion within the cavity so as to establish hydrostatic pressure inside the cavity while the volume of the cavity remains within a few percent of its maximum volume.

Abstract: The liquid slug projector apparatus is entirely pneumatically operated. It comprises a generator having a main housing whose main port fluidly communicates with a liquid body. A first shuttle and a second shuttle are slidably mounted inside the main housing. The first shuttle forms with the main housing a slug chamber for confining therein a liquid slug. A pneumatic source together with a pneumatically-operated valve cyclically cause the shuttles to move relative to or in locked condition with each other, thereby applying during each cycle of operation an abrupt propulsion force to the confined liquid slug which becomes expelled as a very high-velocity liquid jet through the main port.

Abstract: A bi-planar pontoon paravane is towed by a marine vessel and controls the depth and position of a towed seismic source array. The bi-planar pontoon paravane is made up of a buoyant bridge with right and left wings attached to the long sides of the bridge, the wings projecting into the water and, in concert, providing a side force. The paravane is towed by a tow line connected to an adjustable bridle which in turn is connected to the paravane. Remote adjustment of the bridle is provided by an hydraulic valve on the vessel controlling an hydraulic motor and gear arrangement on the paravane to adjust the bridle. Adjustment of the bridle adjusts the angle of attack of the paravane. The paravane provides a housing formed below the bridge and between the two wings for housing the seismic source array. A boom on the vessel is attached to the seismic source array, through the bridge, when the assembly is to be placed in or removed from the water.

Abstract: A float for use in seismic surveys of the sea bed supports a plurality of seismic pulse transmitters (6) which are suspended on lines (7) beneath the float (1). At a distance from the front end of the float (1), on one sidewall thereof, a fastening device for a towing cable and a lead-in for control lines and lines for supplying operating medium to the pulse transmitters are provided. These lines and cables are gathered in a common line (3) which extends behind the tow ship. The line (3), at a distance away from the float (1), is connected to a line (4) which leads to a length-regulating device (12) inside the front section of the float. The float is also provided with at least one motor (10) with a drive shaft (9) leading to hoisting drums (8) for the lines (7) to the respective seismic pulse transmitters (6). Both the motors (10, 12) and the seismic pulse transmitters (6) are connected to the pneumatic supply line.

Abstract: A seismic air gun has a passage between the stem of its shuttle and a baffle, whereby ambient pressure can reach the back of the operating piston. The gun is fired by dumping a small quantity of pressure air from the operating chamber via a solenoid valve to the ambient surroundings. The firing seal is a lip seal. The shuttle is of unitary construction, while the baffle is diametrically split.

Abstract: A marine air gun is advantageously converted into a hydro gun by substitution of two clamp rings and by convenient addition of various parts, allowing normal air gun firing by triggering with usual solenoid valve. In a presently preferred embodiment, a novel firing chamber is also substituted, providing outwardly-facing piston rings and cylinder encircling this chamber. A special clamp is substituted for that which normally secures operating chamber to firing chamber. An outer-cylinder-defining housing is concentric around the firing chamber, with an annular piston sliding in the annular cylinder space defined intermediate the firing chamber and the new outer housing. This annular piston is propelled by the air blast, suddenly ejecting water slugs from ports in the new outer housing. Also added is a pressure-controlled air-vent valve, responsive to air pressure coupled through passages in an adapter mounted between solenoid valve and air gun.

Abstract: A seismic acoustic source for generating acoustic pulses in both solid rock and sedimentary layers on land and in both water, rock and sedimentary layers at sea comprises: two chambers; a high pressure chamber and a low pressure chamber communicating but separated from each other by, for example, a first diaphragm, the low pressure chamber being closed by, for example, a second diaphragm. The high pressure chamber contains gas e.g. helium at high pressure whereas low pressure chamber contains a gas such as carbon dioxide at a lower pressure. The pulse is generated by bursting the diaphragm separating the two chambers whereupon the shock wave generated in the carbon dioxide then travels to the other end of the low pressure chamber and leaves by over-pressure behind the shock bursting the second diaphragm. Repetitive operation may be achieved by replacing the first diaphragm with a shock wave valve and the second with operable valve means such as an iris diaphragm or full-bore gate valve.

Abstract: The far-field pressure signature of an air-gun array is derived from near-field measurements. An array of air guns is deployed in the water at a desired depth. A hydrophone is suspended in the middle of the array at the same depth so that the guns are equidistant from the hydrophone. The lateral spacing between the guns and the sensor is much less than the water depth of the guns. Having fired the guns, the ghost reflection amplitude in the near field will be much less than the amplitude of the direct arrivals and can be ignored. The far-field signature is determined by inverting the observed pressure signature, delaying it in proportion to array depth and adding the inverted, delayed signature back to the original signature.

Abstract: The invention is a multi-port, multi-chamber, tuned, air-powered subsea seismic source. It is suitable for producing a seismic wave in a subsea environment during seismic prospecting. Interconnected pressurized chambers are formed between plates located on a movable shuttle and cylinder walls extending inward from the source housing. The source is fired by moving the shuttle through a stroke and allowing the pressurized air within the air chambers to exit through ports into the surrounding water. A unique seal arrangement in also shown.

Abstract: A method for obtaining far-field signatures of marine source arrays by the downward continuation of near-field data recorded along a short signature streamer of closely spaced hydrophones, located beneath the array. This method has several advantages over conventional far-field signature measurement techniques. The technique can be used in water depths as shallow as 50 meters, it does not require any precise knowledge of the array geometry or of the location of the recording sensors, and it may be used on a shot-by-shot basis to obtain signatures for use in a shot-by-shot signature deconvolution.

Abstract: The invention relates to a method of determining the location in the earth of sub-surface boundaries and/or the acoustic properties of sub-surface features substantially in the absence of the far field source wavelet and noise and with errors due to reflections of sound waves from the water being substantially compensated for. The invention uses point sound sources or arrays thereof at a first depth and then scales the energy, pressure and spacing of a similar source at a second depth to provide data which is used to obtain a seismic record.

Abstract: A device for under-water signalling has a chamber (38) which is normally closed by a replaceable element (39). A cartridge (16) in the device can be fired to release gas into the chamber and rupture the element (39), thus causing a sound wave to travel through the water and releasing the contents of the chamber into the water. When an end cap (13) has been removed to prepare the device for use, water pressure can act on a piston (23) to cause firing of the cartridge.

Abstract: A plurality of control station, watertight, submerged junction boxes are towed at spaced positions located along an airgun array, each junction box for including a microprocessor and data storage transmission capability, and airgun firing circuits to control predetermined airguns. The electrical cable for the array and the air supply lines, as well as the airguns to be controlled, are detachably coupled to respective junction boxes. Thus, the number of airguns in the towed array can be changed quickly and conveniently by coupling or uncoupling junction boxes and the associated airguns. A protective hose sheath extends between successive junction boxes and this hose sheath contains power lines and a communication bus, detachably connected to terminals in successive junction boxes. This hose sheath and interiors of junction boxes are pressurized with low pressure air during towing for excluding water in the event of a leak.

Abstract: A means for terminating of splicing a cable intended for towing air-water guns behind a seismic vessel. The end of the cable, or of each cable section, is guided into the housing of the termination member. The termination is formed with separately located connection sites for the cable components. The cable's tension-relieving wires (3) are guided into a first chamber (I) in the housing and fastened to the supporting structure of the chamber (I), i.e., the housing. The chamber (I) is filled with a water-repellant lubricant. The cable's conductors (9) are guided individually through the first chamber (I) and through a sealed passage (10) in a wall (14) defining a second, watertight chamber (II) which is filled with an electrically insulating, hydrophobic, water-emulsifying liquid. The chamber (II) is also provided with a pressure compensator (8).

Abstract: The liquid slug projector apparatus is entirely pneumatically operated. It comprises a generator having a main housing whose main port fluidly communicates with a liquid body. A first shuttle and a second shuttle are slidably mounted inside the main housing. The first shuttle forms with the main housing a slug chamber for confining therein a liquid slug. A pneumatic source together with a pneumatically-operated valve cyclically cause the shuttles to move relative to or in locked condition with each other, thereby applying during each cycle of operation an abrupt propulsion force to the confined liquid slug which becomes expelled as a very high-velocity liquid jet through the main port.

Abstract: The invention is a device known generically as an "air gun" suitable for producing a shock wave in a subsea environment during seismic prospecting. It is made up of a central chamber holding pressurized gas. The gas is released explosively into the water by moving a double acting shuttle. The shuttle seals the central gas chamber at each end of its stroke. A novel pneumatic actuator is also shown.

Abstract: An air gun of the reciprocating shuttle type includes a split-ring sleeve valve that is expandable against the inner wall of a firing chamber. The sleeve valve encircles the shuttle body. The shuttle body and the sleeve valve include a set of air release orifices that are alignable with a corresponding set of air exhaust ports of the firing chamber.

Abstract: A seismic method and apparatus utilizes two point sound sources located at the same location on the earth to produce sound waves at different amplitudes and times. The reflections of the sound waves are analyzed to determine the acoustic properties and rock boundaries within the earth.

Abstract: In order to determine the signature of an array of n seismic sources 21 to 27, for instance marine seismic sources in the form of air guns, the array is actuated and the emitted pressure wave is measured at n independent points whose positions will respect to the array are known by hydrophones 31 to 37. The measurements are processed to produce n equivalent signatures of the n sources taking into account the interactions therebetween. The signature of the array is then determined merely by superposing the n equivalent signatures.

Abstract: A sleeve shuttle air gun is described which can be fired by a solenoid valve without dumping compressed air into the ambient prior to firing, thereby avoiding the generation of premature impulses caused by such dumping and avoiding the heavy duty complex solenoid dump valves and two-stage dump valves of the prior art. The sleeve shuttle is automatically returned to its initial closed and sealed position after each firing of the airgun by the refilling flow of only one level of pressurized air without a separate low level pressure source to control the sleeve shuttle. A long acceleration path is provided so the sleeve shuttle attains velocity prior to opening the discharge ports for producing a sudden, powerful discharge. The end of the sleeve shuttle travels completely beyond the discharge ports, and is then damped by interaction with damper ports located beyond the discharge ports.

Abstract: A new circuit is added to the old electrical circuit including two electrodes underwater positioned very close to a gas exhausting gun gaseous exhaust such as an air gun, wherein the exhaust from the firing gas exhausting gun momentarily blows away the conductive sea water from one or both of the electrodes to produce a high voltage pulse due to the large increase in resistance in the circuit indicating the precise moment of firing of the gas exhausting gun.This new circuit added to the above circuit is a circuit polarity reversing circuit which includes particularly a positive current generator, a negative current generator, and a sea ground for forming a third electron source when any of the two electrodes becomes defective, thus forming a fail-safe system.

Abstract: New methods are disclosed for detecting the instant of firing of a gas exhausting gun such as an air gun which reduce plating action on two closely spaced apart electrodes submerged underwater very close to the gas exhausting gun exhaust comprising the basic steps of passing a current through the two electrodes, and periodically reversing the current to the two electrodes responsive to a polarity reversing circuit means after (1) a predetermined period of time or (2) after each firing of the gas exhausting gun.Likewise new methods for forming and assembling a fail-safe gas exhausting gun firing detection circuit are set forth in detail.

Abstract: Oxygen and propane are supplied to the combustion chamber of a marine seismic gas exploder from a pair of pressure regulated gas charging cylinders. Ignition of the resultant explosive gas mixture drives a piston connected with means for creating an acoustic disturbance in the water. The outputs from the charging cylinders are fed simultaneously to a mixing manifold connected to a large orifice communicating with the combustion chamber.The ratio of gases in the resultant mixture is automatically determined by the relative volumes and pressures of the charging cylinders, which may be precisely regulated by adjustment of pistons movable within such cylinders and by gas pressure regulation. To safeguard against too rapid voiding of a small volume charging cylinder, voiding of the larger volume cylinder may be initiated first with the aid of a choke downstream of the manifold. This will create an artificial back pressure in the distribution system.

Abstract: The present invention provides a method for determining the spacing and size of air guns in a tuned air gun array. Volume ratios are calculated based upon a predetermined maximum volume for any individual air gun. The volumes are cross-referenced to spacings for optimum air gun interaction. The resulting air gun array operates as a broadband high-energy point source.

Abstract: A compressed-gas seismic energy source suitable for underwater prospecting. The device has two gas storage cylinders placed at the opposite ends of a shuttle. The shuttle seals both storage cylinders when seated at the end of its stroke and releases gas for the desired sonic pulse from both cylinders during its stroke. Design of the device provides for simplicity of operation, ready modification of the sonic signature, and reliability of moving parts.

Abstract: Disclosed herein are improvements in a recoil reducing system of a gas gun which create pulses in a liquid medium by introducing therein gas under high pressure. The release of high pressure gas from the barrel of such a gas gun causes recoil of the barrel. To reduce recoil, a reaction plate is attached to the barrel by metal rods so that the high pressure gas will impinge upon the reaction plate before escaping into the medium, and the force exerted on the reaction plate by the impinging gas will at least partially balance the force of recoil. In a preferred embodiment of this invention, a layer of shock absorbent material is interposed between the reaction plate and the impinging gas to absorb some of the energy of the gas. Flexing of the metal rods is thereby reduced and the life of the rods is extended. Alternatively, the flexing of the rods is reduced by connecting each rod to the reaction plate through a chain link type of connection comprising two rings, each ring passing through the other ring.

Abstract: Methods of detecting the presence and extent of hydrocarbon accumulations in subterranean formations are provided comprising introducing a first gas into the formation having the property of being substantially unreactive with the formation and with water contained therein but forming a combustible mixture with hydrocarbons and introducing a second gas into the formation having the property of being substantially unreactive with the formation and water but being explosively reactive with the first gas when mixed therewith in the presence of hydrocarbons. The second gas is mixed with the first gas in the formation and when in the presence of hydrocarbons the mixture explodes thereby generating seismic waves which travel through the earth to the surface thereof. The seismic waves are detected on the surface to thereby determine the presence and extent of the hydrocarbon accumulations in the subterranean formation.

Abstract: A wide seismic source for use in marine surveys comprising at least two arrays of seismic sources disposed to be towed in a spaced parallel arrangement. Each array includes an elongated float having discrete seismic sources mounted thereon and provided with a steering means to maintain the float in the desired lateral position.

Abstract: A new circuit is added to an electrical circuit including two electrodes underwater positioned very close to an air gun gaseous exhaust wherein the exhaust from the firing air gun momentarily blows away the conductive sea water from one or both of the electrodes to produce a high voltage pulse due to the large increase in resistance in the circuit indicating the precise moment of firing of the air gun free of any uncertainty and mechanical noise which normally affects conventional transducers.This new circuit added to the above circuit is a circuit polarity reversing circuit which includes particularly a positive current generator, a negative current generator, and a sea ground for forming a third electron source when any of the two electrodes becomes defective, thus forming a fail-safe system.

Abstract: Disclosed is a seismic source device, known in the industry as an air gun, having shuttle control for allowing a predetermined discharge of compressed air into water for purposes of seismic exploration. The shuttle is controlled by secondary shuttle means for closing the exhaust ports before all of the compressed air in the firing chamber of the air gun is exhausted. This point of closing the exhaust ports before virtually all of the compressed air is discharged differs from prior art air guns. By preventing further discharge of air, secondary pulses are greatly reduced, thereby enhancing the operation of the entire system. Further, by preventing all the air in the firing chamber from being discharged, the system becomes more efficient and more cost effective.

Abstract: A marine seismic source employs a cylindrical gas exploder adapted to be supported from a surface vessel in a submerged state adjacent a marine bottom. The force of expanding gases within the exploder applies a thrust along the exploder longitudinal axis to a ground contact member operatively interconnected with the exploder to produce a seismic signal. The energy producing force is reacted by piston means within the exploder interconnected rigidly with a large area external water interacting disk. The mass of the reaction piston-disk system is sufficiently great so that the slow moving disk experiences viscous damping in the water and thus generates no significant undesirable secondary seismic signal in the water. The exploder may be oriented horizontally for maximum generation of shear waves or inclined at an acute angle to the vertical for generation of a combination of shear waves and compressional waves.

Abstract: An improved seismic prospecting system comprising the use of a closely spaced sequence of source initiations at essentially the same location to provide shorter objective-level wavelets than are obtainable with a single pulse. In a preferred form, three dynamite charges are detonated in the same or three closely spaced shot holes to generate a downward traveling wavelet having increased high frequency content and reduced content at a peak frequency determined by initial testing.

Abstract: An acoustic impulse generator is disclosed for use in a fluid media for oceanographic, seismographic and related applications. The generator includes a housing with a piston slidably disposed therein and a passageway through which a rod attached to the piston moves. A firing chamber is attached to the housing for channeling a quantity of liquid through a nozzle. A diaphragm may be disposed between the housing and the firing chamber with the quantity of liquid being displaced in response to movement of the piston.

Abstract: The invention relates to a device for propelling a liquid projectile to create a shock wave by implosion, said device comprising a cylinder containing two pistons, a reservoir of pressurized fluid acting on the pistons, a stop for stopping the piston, a perforated connecting piece to permit the escape of the propelled liquid and for connecting the cylinder with a return mechanism. The invention is applied to underwater oil prospecting.

Abstract: An open-ended seismic source for use in a liquid medium such as water is disclosed. The source includes a source of explosive gas, a firing chamber connected to the source, a capacitor discharge ignition system connected to the firing chamber for igniting the gas in the firing chamber, a barrel connected to the firing chamber, defining an explosion chamber and having an outlet at its lower end, a plurality of baffle plates fixed in the barrel near the outlet for permitting the exploded gas to enter the medium and for retarding the entry of the medium into the barrel, and a reaction plate attached to the barrel and disposed below the outlet so that the exploded gas entering the medium impinges on the plate and the recoil of the barrel is reduced.

Abstract: A device for underwater generation of low frequency sound comprising a coally shaped explosion chamber open at both ends, a firing chamber having inlet and outlet passages at opposite ends thereof, ignition means in the firing chamber, a restricted orifice between the outlet passage of the firing chamber and the small open end of the explosion chamber, a mixing chamber opening into said inlet passage, and two supply lines for introducing gases to form a combustible mixture in the mixing chamber, the combined resistance the supply lines and the mixing chamber offer to the flow of gas in the upstream direction being slightly greater than the flow resistance of said restricted orifice, the arrangement being such that when the gases in the firing chamber are ignited with the device submerged in water the flame spreads down stream through the explosion chamber and also upstream into the supply lines thereby extinguishing the flame.

Abstract: A marine gun for the production and timing of underwater pulses by the discharge of gas under pressure comprises a body having at least one port, means retaining the gas in said body under pressure and for allowing it to discharge through said port to produce said pulses, said gun including at least two electrodes which make electrical contact with the water in the path of gas discharged through said port such that such a discharge of gas increases the electrical resistance between said electrodes to produce a timing signal.

Abstract: A seismic source is described which drives one or more jets of high velocity water into an underwater environment and then abruptly terminates the jets. The momentum of the free jet columns generate vapor cavities in the water away from the housing of the source which cavities collapse coherently to generate the seismic signal. A piston and a valve sleeve are slidably mounted in a cylinder in the housing. The piston seals off a volume of gas on its rearward side. The forward side of the piston defines one surface of a chamber. The chamber receives high pressure water from an inlet. In its rearward position, the valve sleeve seals a set of jet apertures in the side of the cylinder. In its forward position the valve sleeve opens the apertures, exposing the chamber interior to the exterior underwater environment. With the valve sleeve in its rearward position with the apertures sealed, the high pressure water entering the chamber moves the piston to its rearward position and compresses the gas.

Abstract: The underwater charge launcher linearly ejects a small, water-propelled explosive charge into the water from the open end of an ejection barrel trailed in the water behind a seismic exploration vessel. The charge is detonated, after a one to two-second delay, when a percussion-ignitable delay cap in the end of the charge impacts a firing member positioned adjacent the open end of the ejection barrel. The firing member includes a firing pin mounted on a rotatable, spring-biased striker plate having a U-shaped rim. When a charge is ejected from the barrel, the primer cap impacts the firing pin. The kinetic force of the ejected charge acting against the firing pin overcomes the moment of inertia of the striker plate, causing it to rotate the firing pin out of the path of the charge. The charge is supported and guided by the unobstructed portion of the U-shaped rim of the striker, as the charge is ejected out of the launcher. After a preset delay, the charge detonates when it is a safe distance from the launcher.